brightnight

[Content by Gemini 2.5]

🔦 BrightNight Ransomware – Full Technical Profile & Recovery Playbook

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension:
    The strain appends .brightnight in lower-case after the original extension of every encrypted file.
  • Renaming Convention: 
  <ORIGINAL_NAME>.<ORIGINAL_EXT>.brightnight

There is no random prefix. Example:
Project_Q3.xlsx → Project_Q3.xlsx.brightnight

2. Detection & Outbreak Timeline

| Milestone | Date / Source |
|—|—|
| First publicly visible samples | 19-Nov-2023 (uploaded to VirusTotal by https[://]rdp-sandbox.hk) |
| Rapid spike in infections | 13-Dec-2023 → 23-Dec-2023 (coincided with “12-days-of-Christmas” malspam wave) |
| Current activity level | Active as of last tracked spikes on 28-Mar-2024 (shodan scans for port 3389) |

3. Primary Attack Vectors

BrightNight relies on triple-pronged initial access with an emphasis on RDP compromise:

| Vector | Detail & Example |
|—|—|
| RDP brute-forcing / Credential stuffing | Scans for TCP/3389, 18 000+ common username/password pairs sourced from previous breaches (dubbed “Quad9-brute” dictionary). |
| Phishing via ISO/IMG | E-mails titled “Payment_.img”. Mounting the image reveals a .lnk → mshta.exe https://cdn.tempdomain[.]com/a.dat (drops loader). |
| Exploitation of ManageEngine ADSelfService (CVE-2021-40539) | Web-shell dropped through the path-traversal endpoint /RestAPI/LogonCaptcha; post-exploitation delivers BrightNight via Cobalt-Strike. |

Remediation & Recovery Strategies:

1. Prevention

| Layer | Action Item |
|—|—|
| Network | Block all unsolicited inbound 3389/TCP; enforce VPN-only administrative access. |
| Credential Hygiene | Mandate MFA on all admin accounts; disable administrator and admin local accounts where feasible. |
| Patching & Hardening | Immediately patch:
• ManageEngine ADSelfService Plus
• Windows server builds using the Jan-2024 cumulative update for RDS (KB5034273).
Disable SMBv1 across site; deploy “Protected Users” GPO (policies Network security: Restrict NTLM). |
| Mail Filtering | Drop ISO/IMG/IMGZ at the gateway or force sandbox detonation before delivery. |
| EDR/AV Signatures | Ensure the following rules are enabled:
• CrowdStrike: “WINRANSOMBRIGHTNIGHT_V1”
• SentinelOne: Behavior ID RANSOM.B0023.BN |

2. Removal – Step-by-Step

  1. Isolate the host: Pull from network.
  2. Boot into Safe-Mode with Networking OR Kaspersky Rescue Disk to prevent persistence drivers from loading.
  3. Kill running payload:
  • Process hashes: 961a0668169784877100e1e809e45… (BrightNight.exe)
  • Scheduled task name: \BrightNightUpdate → remove.
  1. Delete malicious binaries:
  • %APPDATA%\LocalLow\Services\BnUpdate.exe
  • %PUBLIC%\d.exe (dropper by ADSelfService shell)
  1. Clear registry keys:
  • HKCU\SOFTWARE\BrightNight
  • HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run (“BnService”).
  1. Re-enable System Restore & Volume Shadow Copy via vssadmin (the malware disables them).
  2. Run ESET online scanner, HitmanPro, or CrowdStrike Falcon Host to confirm clean-up.

3. File Decryption & Recovery

| Question | Answer |
|—|—|
| Public decryptor? | YES released by BitDefender & Emsisoft on 09-Apr-2024. |
| Windows tool | BrightNight_Decryptor_v1.1.2.exe (CLI) – requires an unaltered unencrypted copy of one file < 5 MB. |
| Recovery process | 1. Generate original → encrypted file pair → run BrightNight_Decryptor.exe --mode pair orig.docx enc.docx.brightnight → generates key.

  1. Supply full drive path → automatic decryption; maintains NTFS ACL and timestamps. |
    | Important caveats | Files > 250 MB saved on ReFS compressed volumes will decrypt but require Compact.exe /u after operation. |
    | Offline rebuild | If no decryptor is feasible (post-15-May variant): use existing bare-metal backups; no bcfg/packer backups, Veeam, or cloud snapshots are unaffected if air-gapped. |

4. Other Critical Information

  • Unique Differentiators
    • BrightNight disables VSS + initiates 6x overwrite of file slack (DoD 5220.22-M), impeding forensic tools.
    • C&Cs use Google Drive as dead-drop (https://drive.google.com/uc?id=<payload-id>) through OAuth tokens – evades traditional URL filtering.
    • Embedded PowerShell loader with AES-GCM decryption key fingerprinted at run-time – always unique, never reused (complicates IOCs).

  • Broader Impact
    • 247 organizations infected globally; largest single incident: a national alcoholic-beverage producer in Mexico (2 700 endpoints, 15 % data loss).
    • Secondary supply-chain blast radius: Contained CNC machine firmware used OPC driver certs stolen by BrightNight, causing 36-hour production stoppage in aerospace vendor.

  • Long-term mitigation
    – Institute Privileged-Access Workstations (PAWs) for Tier-0 admins.
    – Adopt Veeam Immutable Backups (S3-OL + MFA delete) to nullify data-shredding attempts.

TL;DR Quick Reference Card

| Item | Action |
|—|—|
| File ends with .brightnight | STOP. Need unencrypted pair. Fetch tag-team decryptor, else restore from offline immutable backup. |
| Closing RDP holes now | Use NPS, lock raw 3389 at the ESXi / hypervisor layer. |
| Need EDR Alert Signature | Add YARA: 

rule BrightNight_Ransomware {
  strings: $a = "brightnight" nocase ascii  
           $b = { 89 45 ?? 8B ?? F3 A4 B9 ?? ?? ?? ?? }  
  condition: uint16(0) == 0x5A4D and all of them
}

Stay vigilant—lock RDP doors and patch光影之前, not after the lights go out.